Please help!

I'm 31 weeks pregnant with my 2nd daughter. My husband and I am not sure what to name her. Our first daughter is Adelynn which I like because it is not a common name. What do you think of the name Isla? Do you think it sounds ok with Adelynn? Do you think it's too popular? Also does anyone have any ideas for a middle name? Catherine is the name of my great grandmother and also my husbands great grandmother but, does IslaCatherine sound ok? The other problem is our last name starts with the letter Y, so her initials would be ICY or IKY (if her spell it Kathryn).